A problem with many hair dyes is that they cannot be quickly or easily removed from the hair. Permanent dyes can only be removed by bleaching which can damage the hair. Semi-permanent dyes, which penetrate the hair and are capable of giving deep shades, can last up to ten washes with a shampoo after application. Temporary dyes which do not penetrate the hair and which are removed by washing, suffer from several disadvantages. For example, the effect obtained from a rinse-off product is usually slight and is therefore regarded by the consumer as poor value. The depth of color using a temporary dyes can, however, be improved if employed as a leave-on product, but such products are not always fast to water and can rub off onto bedding, causing pillow staining. Hair spray products containing pigments and resins tend to fall off the hair and, for this reason, have not achieved popularity amongst consumers.
Accordingly, there exists a need for a temporary hair dye which is entirely safe to use, simple to apply, rapid in its effect, does not rub off onto bedding and which does not wash off the hair when contacted with water, such as in a rain shower, but which can nevertheless be removed by shampooing to enable a different color or shade to be applied as desired.
It has been proposed in U.S. Pat. No. 3,912,808 (Gillette Company) to employ a composition for waving or straightening hair, which comprises an aqueous solution of a reducing agent, a water-soluble cationic polymer having a molecular weight of from 20,000 to 3,000,000, such as polydiallyldiethylammonium chloride. Optionally, there can also be present in such compositions an amphoteric surfactant, for example, an imidazoline derivative made by condensing polyamines with long chain fatty acids, as well as an acidic, basic, or disperse dye or oxidation dye intermediate. It is however stipulated that when a surface active agent is present in the composition, there must also be present a water-miscible hydroxylated organic primarily aliphatic solvent, such as ethanol, isopropanol or benzyl alcohol.
We have now discovered that hair can be colored temporarily such that the dye applied thereto will be fast to water, but which can be removed by shampooing, by employing a composition which includes a polymer having a relatively high cationic charge and a monomer such as a dye having an anionic charge, preferably also with an amphoteric surfactant and/or a relatively high concentration of an inorganic electrolyte salt, as solubilising agents. Such a composition forms a single liquid phase solution which on dilution with water, such as during application to hair following shampooing forms an insoluble complex of the polymer and dye which adsorbs strongly to hair.
In comparative tests, to be described in detail later in this specification, it is apparent that a far more intense coloration of blonde hair is obtained following application of the composition according to the invention, than when a comparative composition based on the teaching of the Gillette U.S. Pat. No. 3,912,808 is employed.